JP7119689B2 - Manufacturing method of insulated circuit board with heat sink and insulated circuit board with heat sink - Google Patents

Description

The present invention relates to a method for manufacturing an insulating circuit board with a heat sink, in which a heat sink is bonded to an insulating circuit board such as a power module board used in a semiconductor device that controls large currents and high voltages, and an insulating circuit board with a heat sink.

As an insulating circuit board with a heat sink, a heat sink in which a circuit layer is bonded to one side of an insulating layer made of a ceramic substrate such as aluminum nitride, and an aluminum-based heat sink is bonded to the other side via an aluminum plate. is known.
For example, in a power module substrate with a heat sink disclosed in Patent Document 1, a circuit layer is bonded to one surface of a ceramic substrate, and a heat sink is bonded to the other surface of the ceramic substrate via a heat dissipation layer. The top plate portion of the heat sink is formed with a housing recess for housing the insulated circuit board.

JP 2016-181549 A

By the way, it is conceivable to provide a plurality of fins on the bottom surface of the heat sink of the power module substrate with a heat sink disclosed in Patent Document 1 in order to improve the cooling efficiency of the power module substrate. In this case, in the manufacturing process of the heat sink, the height of the fins formed in the central portion of the heat sink may be smaller than the height of the fins formed around it. When a power module substrate is bonded to such a heat sink having fins with different heights, the bonding rate between the heat sink and the power module substrate decreases.
In order to suppress the decrease in the bonding rate, it is conceivable to press a plurality of fins with a cushion material such as a graphite sheet in contact with the fins and press them in the stacking direction. However, the bonding rate between the heat sink and the power module substrate cannot be sufficiently improved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing an insulated circuit board with a heat sink and an insulated circuit board with a heat sink that can improve the bonding rate between the heat sink and the insulated circuit board. .

A method for manufacturing an insulating circuit board with a heat sink according to the present invention comprises: an insulating circuit board having a circuit layer formed on one surface of a ceramic substrate and a metal layer formed on the other surface of the ceramic substrate; A method for manufacturing an insulated circuit board with a heat sink, which is arranged on a surface opposite to a ceramic substrate and has a plurality of fins on one surface, wherein the other surface of the heat sink and the metal layer are bonded together. a heat sink bonding step for bonding, wherein the heat sink has a first region in which the height of the fins is large and a second region in which the height of the fins is smaller than that of the first region; In the joining step, the tip of the fin in the first region is brought into contact with a graphite sheet, and the tip of the fin in the second region is brought into contact with carbon felt having a surface height at least greater than that of the graphite sheet. In this state, the insulating circuit board and the heat sink are pressed.

Here, when each fin of a heat sink comprising a first region having a large fin height and a second region having a smaller fin height than the first region is pressed with one graphite sheet, the graphite sheet does not come into contact with the fins of the second region, or even if it comes into contact with the fins, the pressing force becomes weaker. Therefore, the bonding rate between the portion of the heat sink corresponding to the second region and the insulating circuit board is reduced.
In contrast, according to the manufacturing method of the present invention, when joining the metal layer of the insulated circuit board and the heat sink, the graphite sheet is brought into contact with the tips of the fins in the first region, and the tips of the fins in the second region are brought into contact with each other. Since the insulated circuit board and the heat sink are pressed while the carbon felt, which is taller than the graphite sheet and has high cushioning properties, is in contact with the graphite sheet, the pressing force can be applied evenly to the first region and the second region. It is possible to reliably bond the metal layer of the insulated circuit board and the heat sink and improve the bonding rate.

As a preferred aspect of the method for manufacturing an insulated circuit board with a heat sink according to the present invention, the second region is located in the central portion of the one surface, and the first region is located in the outer peripheral portion of the one surface. I hope you are.
Here, when a heat sink having a plurality of fins is manufactured by forging, it is difficult for the material to spread to the central portion due to the flow of material at that time, so the height of the fins in the central portion tends to be smaller than the height of the fins in the outer peripheral portion. It is in. That is, the second area is located in the central portion of one surface of the heat sink on which the plurality of fins are formed, and the first area is located in the outer peripheral portion.
In the above aspect, the metal layer of the insulated circuit board and the heat sink can be more reliably bonded simply by arranging the graphite sheet on the outer peripheral portion and the carbon felt on the central portion.

In a preferred embodiment of the method for manufacturing an insulated circuit board with a heat sink according to the present invention, a notch is formed in the graphite sheet at a position corresponding to the second region, and the carbon felt is fitted into the notch. .
In the above aspect, since the first region can be pressed only by the graphite sheet and the second region can be pressed only by the carbon felt, the metal layer of the insulating circuit board and the heat sink can be more reliably bonded.

In a preferred embodiment of the method for manufacturing an insulated circuit board with a heat sink according to the present invention, the carbon felt is provided on the graphite sheet.
In the above aspect, since it is not necessary to form a notch for fitting the carbon felt in the graphite sheet, the configuration of the graphite sheet can be simplified.

As a preferred aspect of the method for manufacturing an insulated circuit board with a heatsink of the present invention, the heatsink bonding step may bond the insulated circuit board, in which the circuit layer and the metal layer are bonded to the ceramics substrate, to the heatsink.
Here, when a laminate obtained by laminating a circuit layer, a ceramic substrate, a metal layer, and a heat sink in this order is pressed in the lamination direction to bond them, there are many bonding sites, so bonding positions may shift.
On the other hand, in the above-described aspect, the insulated circuit board with the heat sink can be manufactured only by joining the heat sink to the insulated circuit board in which the circuit layer and the metal layer are joined to the ceramic substrate. It is possible to improve the reliability of the insulated circuit board with the heat sink.

In a preferred embodiment of the method for manufacturing an insulated circuit board with a heat sink of the present invention, the height of the carbon felt is 0.05 mm or more and 1.0 mm or less greater than the surface of the graphite sheet.

An insulating circuit board with a heat sink of the present invention comprises: an insulating circuit board having a circuit layer formed on one surface of a ceramic substrate and a metal layer formed on the other surface of the ceramic substrate; and the ceramic substrate having the metal layer. is arranged on the opposite surface, and has a heat sink having a plurality of fins on one surface, wherein the insulating circuit substrate is provided on the other surface side of the heat sink via a joint portion. and the heat sink includes a first region in which the height of the fins is large and a second region in which the height of the fins is smaller than that of the first region. When the bonding rate is 95% or more, the area of the circuit layer is A, the warp amount of the circuit layer is Z, and the concave deformation on the bonding surface side of the circuit layer is a positive warp amount, A and Z ratio Z/A is in the range of 0 μm/cm ² or more and 10 μm/cm ² or less.
In this insulating circuit board with a heat sink, the bonding ratio between the insulating circuit board and the heat sink is 95% or more, and the warpage amount Z of the circuit layer/the area A of the circuit layer is in the range of 0 μm/cm ² or more and 10 μm/cm ² or less. Therefore, it is possible to suppress the generation of voids and the like during soldering when electronic components such as chips are fixed onto the circuit layer of the insulated circuit board with a heat sink.

In a preferred embodiment of the insulated circuit board with a heat sink of the present invention, the circuit layer comprises a first circuit layer made of pure aluminum formed on the ceramic substrate and an aluminum alloy formed on the upper surface of the first circuit layer. and a second circuit layer comprising: the metal layer made of pure aluminum; and the heat sink made of an aluminum alloy.
In the above aspect, the first circuit layer and the metal layer formed on both sides of the ceramic substrate are made of pure aluminum, and the heat sink and the second circuit layer are made of an aluminum alloy. can be balanced and warpage can be reduced.

According to the present invention, the bonding rate between the heat sink and the insulated circuit board can be improved.

1 is a cross-sectional view showing a power module using an insulated circuit board with a heat sink according to one embodiment of the present invention; FIG. FIG. 2 is a plan view of an insulating circuit board with a heat sink according to the embodiment; 1. It is sectional drawing explaining the manufacturing method of the insulated circuit board with a heat sink shown in FIG. 1, (a) shows the state before joining an insulated circuit board and a heat sink, (b) shows the state after joining. FIG. 11 is a cross-sectional view showing a support plate used when joining the insulated circuit board with a heat sink according to the modified example of the embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Schematic Configuration of Insulated Circuit Board with Heat Sink]
As shown in FIG. 1, an insulating circuit board 1 with a heat sink manufactured by the method for manufacturing an insulating circuit board with a heat sink according to the present invention is a fin-integrated heat sink in which a plurality of fins are erected on an insulating circuit board 10. 20 are joined together.

The insulating circuit board 10 is a so-called power module board, as shown in FIG. Become. The element 30 is an electronic component including a semiconductor, and various semiconductor elements such as an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and an FWD (Free Wheeling Diode) are selected. In this case, although illustration is omitted, the element 30 is provided with an upper electrode part on the upper part and a lower electrode part on the lower part, and the lower electrode part is joined to the upper surface of the circuit layer 12 by solder 31 or the like. Thus, the element 30 is mounted on the top surface of the circuit layer 12 . Further, the upper electrode portion of the element 30 is connected to the circuit electrode portion of the circuit layer 12 through a lead frame or the like joined by solder or the like, and the power module 100 is manufactured.

[Configuration of insulation circuit board]
The insulating circuit board 10 includes a ceramic substrate 11 , a circuit layer 12 formed on one surface of the ceramic substrate 11 , and a metal layer 13 formed on the other surface of the ceramic substrate 11 .
The ceramic substrate 11 is an insulating material that prevents electrical connection between the circuit layer 12 and the metal layer 13, and is made of, for example, aluminum nitride (AlN), silicon nitride _{( Si3N4} ), alumina _{( Al2O3} ). etc., and its thickness is 0.2 mm to 1.2 mm.

The circuit layer 12 is composed of a plurality of small circuit layers separated by circuit patterns, and includes a first circuit layer 121 bonded to the ceramic substrate 11 and a second circuit layer 122 bonded to the upper surface of the first circuit layer 121. It has The area A of such a circuit layer 12 is set to 49 cm ² , for example.
Of these, the first circuit layer 121 is made of pure aluminum with a purity of 99% by mass or more, and according to the JIS standard, pure aluminum in the 1000s, especially 1N90 (purity of 99.9% by mass or more: so-called 3N aluminum) or 1N99 (purity 99.99% by mass or more: so-called 4N aluminum) can be used.
The metal layer 13 is made of pure aluminum or an aluminum alloy with a purity of 99% by mass or more, and JIS standard 1000 aluminum, particularly 1N99 (purity of 99.99% by mass or more: so-called 4N aluminum) can be used.

In the present embodiment, the first circuit layer 121 and the metal layer 13 are aluminum plates made of rolled plates of pure aluminum (so-called 4N aluminum) with a purity of 99.99% or more, and the thickness thereof is 0.4 mm to 0.4 mm. The thickness is set to 1.6 mm, and the thickness dimension of the first circuit layer 121 and the thickness dimension of the metal layer 13 are set to be the same.
On the other hand, the second circuit layer 122 is made of an aluminum alloy such as A6063 series, and its thickness is set to 0.5 mm to 1.5 mm. They are set to the same thickness dimension.
The circuit layer 12 and the metal layer 13 are formed by, for example, Al—Si-based or Al—Si—Mg-based wax in the order of the first circuit layer 121, the second circuit layer 122, the ceramics substrate 11, and the metal layer 13. They are joined by stacking them with materials interposed therebetween and applying pressure in the stacking direction and heating them.

[Heat sink configuration]
The heat sink 20 joined to the insulating circuit board 10 is formed by forging an aluminum alloy such as A6063 series. A housing recess 21 for housing at least a portion of the insulating circuit board 10 is formed in the central portion of the heat sink bonded to the metal layer 13, and a thick portion is left on the outer peripheral side of the housing recess 21 to form a peripheral wall. A portion 23 is formed. The metal layer 13 of the insulating circuit board 10 is laminated on the bottom surface 22 of the housing recess 21 via an Al-Si-Mg-based brazing material. A heat sink 20 is bonded.

In the heat sink 20 , the thickness dimension of the accommodation recess 21 (thickness dimension of the bottom surface 22 of the accommodation recess 21 ) is formed thinner than the thickness dimension of the peripheral wall portion 23 . For example, the heat sink 20 is formed of a plate material made of an A6063 series aluminum alloy with a total thickness of 2.1 mm to 6.8 mm, the thickness dimension of the peripheral wall portion 23 is 2.1 mm to 6.8 mm, and the thickness dimension of the bottom surface 22 of the accommodation recess 21 is is set between 0.5 mm and 1.5 mm.

A plurality of pin-shaped fins 25 are erected on a surface 22 b of the housing recess 21 of the heat sink 20 opposite to the bottom surface 22 . Therefore, as shown in FIGS. 2 and 3, a first region Ar1 in which the height of the pin-shaped fins 25 is large and a second region Ar2 in which the height of the pin-shaped fins 25 is smaller than that of the first region Ar1 are provided. ing. Specifically, since the heat sink 20 is formed by forging, as shown in FIG. A second region Ar2 in which the height of the pin-shaped fins 25 is small is arranged in the central portion. The height of the pin-shaped fins 25 in the first region Ar1 is 0.5 to 10 mm, and the height of the pin-shaped fins 25 in the second region Ar2 is 0.4925 to 9.975 mm. The difference is about 25-75 μm.
The shape of the fins erected on the heat sink 20 is not particularly limited, and in addition to the pin-shaped fins 25 as in the present embodiment, diamond-shaped fins, strip-shaped fins, or the like can be formed.

Next, a method for manufacturing the insulating circuit board 1 with a heat sink according to this embodiment will be described.
The manufacturing method includes an insulating circuit board forming step of joining the circuit layer 12 and the metal layer 13 to the ceramic substrate 11 to form the insulating circuit board 10, and a heat sink joining step of joining the heat sink 20 to the insulating circuit board 10. Become. The order of steps will be described below.

(Insulated circuit board forming process)
The first circuit layer 121, the ceramic substrate 11, and the metal layer 13 are laminated with Al—Si brazing filler metal foil interposed therebetween, and the laminate is heated while being pressed in the lamination direction, and then cooled. A first circuit layer 121 is bonded to one surface 11a of the ceramic substrate 11, and a metal layer 13 is bonded to the other surface 11b. The brazing filler metal foil is melted by heating and diffused into the circuit layer 12 and the metal layer 13 to firmly join them to the ceramic substrate 11 .
The bonding conditions at this time are not necessarily limited. A minute or less is preferred. Also, the Al--Si based brazing filler metal foil should preferably have a thickness of 5 μm to 15 μm. Furthermore, in addition to Al-Si-based brazing materials, Al-Ge-based, Al-Cu-based, Al-Mg-based, Al-Mn-based, or Al-Si-Mg-based brazing materials, clad materials thereof, etc. can be used. can also

Then, the second circuit layer 122 is placed on the first circuit layer 121 via an Al--Si brazing filler metal foil, and the first circuit layer 121 and the second circuit are separated by heating while being pressed in the stacking direction. and layer 122 . The pressure in the stacking direction is preferably 0.1 MPa to 0.5 MPa, and the heating temperature is maintained at 590° C. or higher and 615° C. or lower for 3 minutes or longer and 20 minutes or shorter.
As a result, the insulating circuit board 10 in which the circuit layer 12 and the metal layer 13 are bonded to both surfaces of the ceramic substrate 11 is formed.

(Heat-sink bonding process)
As shown in FIG. 3(a), an Al--Si brazing filler metal foil 14 is interposed between the lower surface of the metal layer 13 of the insulating circuit board 10 and the bottom surface 22 of the housing recess 21 of the heat sink 20, and as shown in FIG. ), the metal layer 13 and the heat sink 20 are bonded by heating while being pressed in the stacking direction by the pressure plates 61A and 61B and the support 62 comprising the graphite sheet 64 and the carbon felt 65. .

(Structure of pressure plate)
As shown in FIG. 3B, the pressing plates 61A and 61B are arranged to face each of the small circuit layers constituting the circuit layer 12 formed on the insulating circuit board 10, and press the circuit layer 12. do. Each of the pressure plates 61A and 61B is, for example, a carbon plate laminated on the surface of a prismatic stainless steel material.
In the example of FIG. 3B, two pressure plates 61A and 61B are used to press the circuit layer 12. However, the present invention is not limited to this. may be pressed by three or more pressure plates, or may be pressed by a single pressure plate having a size capable of collectively pressing all the small circuit layers.

(Structure of support plate)
The support 62 includes a support plate 63 made of stainless steel, and a graphite sheet 64 and carbon felt 65 fixed to the upper surface of the support plate 63 . The carbon felt 65 is made of carbon fiber and is a substantially rectangular plate-like member arranged in the center of the support plate 63 . A graphite sheet 64 is arranged around the carbon felt 65 .
The graphite sheet 64 is arranged to face the pin-shaped fins 25 located in the first region Ar1, and the carbon felt 65 is arranged to face the pin-shaped fins 25 located in the second region Ar1. Specifically, a position corresponding to the second region Ar2 in the graphite sheet 64 is notched in the same shape as the second region Ar2, and the carbon felt 65 is fitted in the notch 651 . That is, the graphite sheet 64 is formed in the same shape as the first region Ar1 shown in FIG. 2 in plan view, and the carbon felt 65 is formed in the same shape as the second region Ar2 shown in FIG. 2 in plan view.

Further, since the pin-shaped fins 25 in the first region Ar1 are longer than the pin-shaped fins 25 in the second region Ar2, the height of the surface of the carbon felt 65 with respect to the surface of the graphite sheet 64 is 0.05 mm or more. 0 mm or less. For example, the thickness of the graphite sheet 64 is set to 1.0 mm, the thickness of the carbon felt 65 is set to 2.0 mm, and the height of the surface of the carbon felt 65 with respect to the surface of the graphite sheet 64 is 1 mm. .0 mm higher.
Note that the thickness of the graphite sheet 64 and the thickness of the carbon felt 65 are not limited to this, and can be changed as appropriate according to the height difference of the pin-shaped fins 25 in the regions Ar1 and Ar2. thickness is greater than the thickness of the graphite sheet 64 .

Further, each of the graphite sheet 64 and the carbon felt 65 has excellent cushioning properties. For example, the graphite sheet 64 has a compression rate of 47%, a recovery rate of 15%, and a stress relaxation rate of 1.0%, and the carbon felt 65 has a compression rate of 55%, a recovery rate of 70%, and a stress relaxation rate of 2.0%. be. That is, the carbon felt 65 is a material having a higher cushioning property than the graphite sheet 64. The carbon felt 65 presses the pin-shaped fins 25 of the second region Ar2, and the graphite sheet 64 presses the first region Ar1. As a result, the pressing force applied to each of the first area Ar1 and the second area Ar2 is substantially uniform.

The heat sink 20 is bonded to the insulating circuit board 10 by sandwiching the insulating circuit board 10 and the heat sink 20 between the pressure plates 61A and 61B and the supporting member 62 and pressing them in the stacking direction. That is, the insulating circuit board 10 is arranged (fixed) via a joint portion on the other surface side (the bottom surface 22 of the housing recess 21) of the heat sink 20 having a plurality of fins 25 on one surface 22b.
The pressure in the stacking direction is preferably 0.1 MPa to 0.5 MPa, and the heating temperature is maintained at 590° C. or higher and 615° C. or lower for 3 minutes or longer and 20 minutes or shorter. Also, the Al--Si based brazing filler metal foil should preferably have a thickness of 5 μm to 15 μm. Further, in addition to the Al-Si brazing material, Al-Ge, Al-Cu, Al-Mg, Al-Mn, or Al-Si-Mg brazing materials, and clad materials thereof may also be used. can.

The insulating circuit board 1 with a heat sink that has undergone various processes as described above has a bonding rate of 95% or more between the insulating circuit board 10 and the heat sink 20. Let A be the area of the circuit layer 12, and Z be the amount of warpage of the circuit layer 12. When the concave deformation on the bonding surface side of the circuit layer 12 is defined as a positive amount of warp, the ratio Z/A between A and Z is within the range of 0 μm/cm ² or more and 10 μm/cm ² or less.
Therefore, it is possible to suppress the generation of voids and the like during soldering when electronic components such as chips are fixed on the circuit layer of the insulating circuit board 1 with a heat sink.
In addition, by forming the first circuit layer 121 and the metal layer 13 bonded to both surfaces of the ceramic substrate 11 from pure aluminum, and forming the heat sink 20 and the second circuit layer 122 from an aluminum alloy, both sides of the ceramic substrate 11 are It is possible to balance the constituent materials of and reduce warpage.

Here, each pin-shaped fin 25 of the heat sink 20 having a first region Ar1 in which the height of the pin-shaped fin 25 is large and a second region Ar2 in which the height of the pin-shaped fin 25 is smaller than that of the first region Ar1 is When pressed with one graphite sheet, the graphite sheet does not come into contact with the pin-shaped fins 25 of the second region Ar2, or even if it comes into contact, the pressing force becomes weak. Therefore, the bonding rate between the portion of the heat sink 20 corresponding to the second region Ar2 and the insulating circuit board 10 is lowered.
In contrast, according to the manufacturing method of the present embodiment, when the metal layer 13 of the insulating circuit board 10 and the heat sink 20 are joined, the graphite sheet 64 is brought into contact with the tips of the pin-shaped fins 25 in the first region Ar1. The insulating circuit board 10 and the heat sink 20 are pressed in a state in which the carbon felt 65, which is taller than the graphite sheet 64 and has high cushioning properties, is brought into contact with the tips of the pin-shaped fins 25 in the second region Ar2. , the pressing force can be applied evenly to the first area Ar1 and the second area Ar2, and the metal layer 13 of the insulated circuit board 10 and the heat sink 20 can be reliably bonded to improve the bonding rate.

Further, the metal layer 13 of the insulated circuit board 10 and the heat sink 20 can be securely attached to the metal layer 13 of the insulated circuit board 10 simply by arranging the graphite sheet 64 on the outer peripheral portion of the upper surface of the support 62 (support plate 63) and arranging the carbon felt 65 on the central portion. can be joined to In this case, since the carbon felt 65 is fitted in the notch 651 formed in the graphite sheet 64, the first region Ar1 is pressed only by the graphite sheet 64, and the second region Ar2 is pressed only by the carbon felt 65. , the metal layer 13 of the insulated circuit board 10 and the heat sink 20 can be bonded more reliably.
Furthermore, since the insulated circuit board 1 with a heat sink can be manufactured only by bonding the heat sink 20 to the insulated circuit board 10 in which the circuit layer 12 and the metal layer 13 are bonded to the ceramic substrate 11, for example, compared to the case of bonding these simultaneously Therefore, it is possible to suppress the displacement of these bonding positions and improve the reliability of the insulated circuit board 1 with a heat sink.

In addition, detailed configurations are not limited to those of the embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, in the above embodiment, the insulating circuit board 10 and the heat sink 20 are joined in the heat sink joining process, but the invention is not limited to this. For example, after bonding the first circuit layer 121 and the metal layer 13 to the ceramic substrate 11, a brazing filler metal foil is placed on the first circuit layer 121 and between the metal layer 13 and the heat sink 20. Then, the second circuit layer 122 and the heat sink 20 may be bonded at the same time.

FIG. 4 is a cross-sectional view showing a support 62A used when bonding the insulated circuit board 10 and the heat sink 20 according to the modification of the above embodiment.
In the above embodiment, the support member 62 is formed in a state in which the carbon felt 65 is fitted in the notch portion 651 of the graphite sheet 64 in which the notch portion 651 having the same shape as the second region Ar2 is formed on the upper surface of the support plate 63. Although it was decided to fix, it is not limited to this.
In this modification, a rectangular graphite sheet 64A is fixed on the upper surface of the support plate 63, and a carbon felt 65A is fixed on the upper surface of the graphite sheet 64A. Specifically, the carbon felt 65A is set to have a thickness (for example, 0.1 mm) that is half the thickness of the above embodiment, and is located on the upper surface of the graphite sheet 64A facing the first region Ar1 of the heat sink 20. is fixed to
In this modified example, the graphite sheet 64A can be formed in the shape of a single rectangular plate. For example, unlike the above-described embodiment, there is no need to provide a space having the same shape as the second region Ar2 in the center. configuration can be simplified.

As an insulating circuit board, a first circuit layer made of 4N aluminum, A6063 series aluminum, was formed on one surface of a ceramic substrate of silicon nitride (Si ₃ N ₄ ) having a size of 70 mm × 70 mm and a thickness of 0.32 mm in a plan view. A second circuit layer made of an alloy and a metal layer made of 4N aluminum bonded to the other surface are used, and in the central part, a recess of 72 mm × 72 mm in plan view and a depth of 3.2 mm is formed, The outer diameter of the peripheral wall portion is 100 mm × 100 mm, the thickness is 4 mm, a plurality of pin-shaped fins are formed by forging on the surface facing the bottom surface of the accommodation recess, the height of the first region is 8.0 mm, and the height of the second region is 8.0 mm. A heat sink made of A6063 series aluminum alloy with a thickness of 7.95 mm was joined.
In joining the insulating circuit board and the heat sink, the circuit layer (second circuit layer) of the insulating circuit board is pressed by the same pressure plate as in the above embodiment, and the plurality of pin-shaped fins of the heat sink are made of stainless steel. The support was supported by a support plate having a cushion material shown in Table 1 fixed on the upper surface of the support. Conditions such as pressure and temperature are the same as in the above embodiment.

For the insulating circuit boards with heat sinks bonded by the procedure shown in Table 1, the amount of warpage of the upper surface of the circuit layer of the insulating circuit boards was calculated, and the bonding ratio between the insulating circuit boards and the heat sink was evaluated.

(Amount of warpage on the upper surface of the circuit layer)
The flatness of the upper surface was determined by measuring the four corners of the circuit layer in the shape of an island with a three-dimensional measuring instrument, using the four corners of the entire surface of the circuit layer as a reference plane, and measuring the Z-axis coordinates. Then, the difference between the maximum value of the Z-axis coordinates and the minimum value of the Z-axis coordinates was calculated as the amount of warpage Z. The measurement area was the total area A covering the four corners of the entire surface of the circuit layer. The ratio Z/A was calculated from these and listed in Table 1.

(Evaluation of bonding rate)
The bonding rate was evaluated by measuring the interface between the metal layer and the heat sink using an ultrasonic flaw detector (FINESAT manufactured by Hitachi Power Solutions Co., Ltd.) and calculating from the following formula. In the image obtained by binarizing the ultrasonic flaw detection image, the non-bonded area is shown in white, so the area of this white part was defined as the non-bonded area. Table 1 shows the results.
(Bonding rate) (%) = {(bonded area) - (non-bonded area)} / (bonded area) x 100
A bonding rate of 95% or more was evaluated as good, and a bonding rate of less than 95% was evaluated as bad.

As is clear from Table 1, in a state in which the tip of the pin-shaped fin in the first region is brought into contact with the graphite sheet and the tip of the pin-shaped fin in the second region is brought into contact with the carbon felt, the insulated circuit board and the In Examples 1, 2, and 3 in which the heat sink was pressed, it was found that an insulated circuit board with a heat sink having a small amount of warping of the circuit layer and a high bonding ratio was obtained.

On the other hand, in Comparative Example 1, since the pin-shaped fins in the first region and the second region were pressed by the graphite sheet, although the amount of warpage and the Z/A value of the circuit layer were the smallest, the cushioning property was lower than that of the carbon felt. Also, the bonding rate was evaluated as "no""x". Further, in Comparative Example 2, since the pin-shaped fins in the first region and the second region were pressed by the carbon felt, the amount of warpage of the upper surface of the circuit layer was 1000 μm, and Z/A was 12.5 μm/cm ² . The evaluation of the bonding rate was negative "x".

Reference Signs List 1 Insulated circuit board with heat sink 10 Insulated circuit board 11 Ceramic substrate 12 Circuit layer 121 First circuit layer 122 Second circuit layer 13 Metal layer 14 Brazing foil 20 Heat sink 21 Accommodating recess 22 Bottom surface 22b Surface 23 Peripheral wall 25 Pin-like fins 30 Element 31 Solder 61A 61B Pressure plate 62 62A Support 63 Support plate 64 64A Graphite sheet 65 Carbon felt 651 Notch

Claims (8)

an insulating circuit board having a circuit layer formed on one surface of a ceramic substrate and a metal layer formed on the other surface of the ceramic substrate; A method for manufacturing an insulated circuit board with a heat sink, comprising a heat sink having a plurality of fins on the surface of the
A heat sink bonding step of bonding the other surface of the heat sink and the metal layer,
The heat sink has a first region in which the height of the fins is large and a second region in which the height of the fins is smaller than that of the first region,
In the heat sink bonding step, a graphite sheet is brought into contact with the tips of the fins in the first region, and carbon felt having a surface height at least greater than that of the graphite sheet is brought into contact with the tips of the fins in the second region. A method for manufacturing an insulated circuit board with a heat sink, wherein the insulated circuit board and the heat sink are pressed while they are in contact with each other. 2. The insulation circuit with a heat sink according to claim 1, wherein the second area is located in the central portion of the one surface, and the first area is located in the outer peripheral portion of the one surface. Substrate manufacturing method. 3. The method for manufacturing an insulated circuit board with a heat sink according to claim 2, wherein the graphite sheet is cut at a position corresponding to the second region, and the carbon felt is fitted into the cutout. . 3. The method of manufacturing an insulated circuit board with a heat sink according to claim 2, wherein the carbon felt is laid on the graphite sheet. 5. The heat sink bonding step includes bonding the insulated circuit board, in which the circuit layer and the metal layer are bonded to the ceramic substrate, to the heat sink. A method for manufacturing an insulated circuit board with a heat sink according to claim 1. 4. The insulating circuit board with a heat sink according to claim 1, wherein the surface of the carbon felt is higher than the surface of the graphite sheet by 0.05 mm or more and 1.0 mm or less. Production method. an insulating circuit board having a circuit layer formed on one surface of a ceramic substrate and a metal layer formed on the other surface of the ceramic substrate; An insulated circuit board with a heat sink, comprising a heat sink having a plurality of fins on the surface of the
The insulating circuit board is arranged on the other surface side of the heat sink via a joint,
The heat sink comprises a first region in which the height of the fins is large and a second region in which the height of the fins is smaller than that of the first region,
A bonding ratio between the insulating circuit board and the heat sink is 95% or more, the area of the circuit layer is A, the amount of warpage of the circuit layer is Z, and concave deformation on the bonding surface side of the circuit layer is positive warpage. An insulated circuit board with a heat sink, wherein the ratio Z/A between A and Z is in the range of 0 μm/cm ² or more and 10 μm/cm ² or less. The circuit layer comprises a first circuit layer made of pure aluminum formed on the ceramic substrate, and a second circuit layer made of an aluminum alloy formed on the upper surface of the first circuit layer,
8. The insulated circuit board with a heat sink according to claim 7, wherein the metal layer is made of pure aluminum, and the heat sink is made of an aluminum alloy.

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